When asked for a source to support his assertion, West referred The Conversation to a BBC article published in October 2015 that said:

Prof Tamara Galloway of Exeter University quotes research estimating that anyone consuming an average amount of seafood would ingest about 11,000 plastic particles a year.

The Conversation asked Galloway, a professor of ecotoxicology, to clarify and provide sources. She said by email:

The stats came from another published paper, by [Belgium-based researchers] Van Cauwenberghe and Janssen in which the authors had made a Fermi estimate (or order of magnitude estimate) based on their field data for cultured shellfish.

I’ve attached the paper on which they based this, and also a copy of a commentary I’ve just written with a colleague which is due to appear in PNAS this week.

It covers a similar topic, but includes some data from another paper too, in which the authors found even higher concentrations of microplastics in seafood. Clearly, there is going to be variation in the levels of contamination depending on location and local sources of pollution, ocean conditions, etc. This does suggest however, that the Van Cauwenberghe results are not just a one off.

As a further comment, we’ve been amazed (having worked in this area for the last 10 years or so), that every single seawater sample that we’ve analysed from anywhere in the world during that time has had microscopic plastic particles in it. But it’s such an easy problem to solve: all we need to do is stop chucking so much rubbish into the oceans.